West Nile Virus

Description of virus that causes the disease.

• virons consist of an envelop and a nucleocapsid
• virons are spherical and measure 40-50 nm in diameter 
• the envelop has surface projections
• the core is isometric and has a diameter of 25-30 nm
• the capsid shells of virons are single layer

West Nile Virus

Viral Specificity:

• its a illness that is spread from mosquito's to humans
• the mosquito bites the host and transmits the virus into the blood
• it cannot be passed from human to human
• the virus travels through the blood stream and affects the different organs in the human body
• it affects the central nervous system

Symptoms and progression of the disease:

West Nile virus produces three different outcomes:

• asymptomatic infection
• mild febrile syndrome (West Nile Fever)
• neuroinvasive disease (West Nile meningitis or encephalitis)
• the ratio for these three stages is roughly 110:30:1

The second febrile stage has an incubation period of 2 to 8 days
symptoms of this stage include:

• drowsiness, pain in joints, rash, swollen lymph node, weakness
• headache, chills, diaphoresis,
• symptoms usually resolve within 7 to 10 days
• fatigue can persist for weeks
• swollen lymph nodes can last up to 2 months

Rarer outbreaks (encephalitis)

• similar early symptoms but also decreased level of consciousness
• spinal cord could get infected
• hepatitis, myocarditis, nephritis, pancreatitis
• recovery is long

Common Methods of Transmission:

• The virus is transmitted through mosquito's vectors
• mosquito's feed on infected birds
• s get West Nile Virus form Birds
• infected mosquito's feed on humans
• Asian tiger mosquito has been found to be a vector of WNV
• virus does not multiply as readily in mammals
• mammals are dead-end infection (doesn't spread any further)

Treatment and Prevention (if any):

• AMD3100 this drug was originally made for HIV but has shown promise against WNV encephalitis
• there have been attempts to use ribavirin, intravenous immunoglobulin, or alpha interferon to treat infections
• There is no vaccine for WNV
• minimize your time out doors when mosquito's are most active
• where long sleeve shirts
• use insect repellent
• make sure your screens on doors and windows are put on tight
• reduce mosquito's breeding areas (clean out any small pool of water)

Miscellaneous:

• WNV emerged as a distinct virus around 1000 years ago
• WNV was posted as one of the possible cause of Alexander the Greats death
• WNV was first isolated from a feverish 37 year old women in the West Nile District of Uganda in 1937
• The first appearance of WNV was in the western hemisphere was in 1999
• A high level of media coverage through out 2001/2002 raised public awareness

Resources accessed:

Wikipedia
CBC News-health-West Nile Virus
www.ictvdb.org